Buried Voltage Blocking Region in Drain-Extended MOS Transistors
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Solution Overview
Problem
Existing drain-extended MOS transistors, particularly DE-PMOS transistors, are limited to a breakdown voltage of less than 50 V, making them unsuitable for certain high-voltage applications.
Innovation Solution
A junction-terminated drain-extended MOS transistor is developed, featuring a buried voltage blocking region and a junction termination diode that provides breakdown protection, allowing the transistor to operate at higher source voltages by forming a spatially diffuse depletion region and distributing the voltage drop across a controlled distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional DE-PMOS transistor structure is used, then the device can be manufactured with standard processes, but the breakdown voltage is limited to less than 50 V
Solution Approach 1:
A buried voltage blocking region of second conductivity type is introduced as an intermediary element between the body well and the substrate contact well. This region acts as a mediator to distribute and block high voltage stress, enabling the transistor to operate at breakdown voltages exceeding 50 V while maintaining compatibility with standard manufacturing processes
Solution Approach 2:
The voltage blocking capability is enhanced by extending the depletion region control into the vertical dimension through the buried voltage blocking region. This adds a depth component to the voltage distribution mechanism, allowing high voltage blocking without increasing the lateral footprint of the device
2Adaptability or versatility
If the breakdown voltage is increased above 50 V, then the transistor becomes suitable for high-voltage applications, but the device structure becomes more complex
Solution Approach 1:
The transistor structure is segmented into distinct functional regions: the body well, the buried voltage blocking region, and the substrate contact well. This segmentation allows each region to be optimized for its specific function while maintaining overall structural simplicity and compatibility with standard fabrication processes
3Reliability
If a buried voltage blocking region is added to increase breakdown voltage, then high-voltage operation is enabled, but the manufacturing process becomes more complex
Solution Approach 1:
The buried voltage blocking region serves multiple functions simultaneously: it provides voltage blocking capability, extends the depletion region control, and can be integrated with existing well formation processes. This multi-functionality allows high-voltage operation to be achieved without proportionally increasing manufacturing complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables the transistor to operate at higher source voltages, providing enhanced high-voltage blocking capabilities and preventing breakdown, thus expanding its suitability for diverse high-voltage applications.
Implementation Method 1
forming a spatially diffuse depletion region
Implementation Method 2
provides breakdown protection, allowing the transistor to operate at higher source voltages by forming a spatially diffuse depletion region and distributing the voltage drop across a controlled distance
Data Source
AI summary
A semiconductor device includes a MOS transistor located within a semiconductor substrate of a first conductivity type. The transistor includes a body well located between a drain well and a substrate contact well. A buried voltage blocking region of a second conductivity type is located within the substrate and is connected to the body well. The buried voltage blocking region extends toward the substrate contact well, with an unmodified portion of the substrate remaining between the voltage blocking region and the substrate contact well.